Currently, spent CD (Compact Disc) substrate is typically made of optical-grade polycarbonate (PC) because of its high-performance chemical properties, such as high transparency, high mechanical strength, low water absorption, low cost and easy to handle when comparing with other substrate materials. Taiwan is one of the biggest producers of compact discs in the world, producing 5.5 billions a year (about 80% of the world market). Defective discs make up about 5-8 percent of production during the manufacturing process, i.e., nearly 600 million discs weighed at least 4,200 metric tons per year. Waste or spent compact discs are typically treated by breaking process, grinding (polishing) process or sandblasting process to separate the metal from plastic parts of the discs. The separated PC resin can be used to blend with other plastic materials or as recycled materials.
For example, the Bayer Group in Germany mainly utilizes the recycled PC in three ways: (1) reselling—15% of the recycled PC is sold to the downstream manufacturers as PC-CD substrate for injection-molding or blending; (2) recycled—65% of the recycled PC is blended with high-molecular-weight PC to form material of certain specification suitable for customers' injection-molding need; (3) plastic composite—20% of the recycled PC is combined with different kinds of plastic to form plastic composite. However, the Bayer recycled PC is only utilized as recycled materials but not regenerated for new uses.
Therefore, the present invention provides a novel process for the chemical recycling of spent PC discs or polycarbonate (PC) waste into bis-alkoxylated diols of bisphenol A, useful polymer intermediates, to meet the industry's requirement and find brand new uses for the spent PCs.